1. Field of the Invention
The field of the present invention is improvements of heat resistant slide members for internal combustion engines, such as an intake valve and a piston ring.
2. Description of the Prior Art
Such conventional piston rings have been formed from an iron-based material such as a cast iron, a spring steel, a stainless steel, etc., (see "Piston Ring" issued from Nikkan Kogyo Newspaper Co., Ltd., for example).
Recently, the internal combustion engines are being designed for increased rotation speed and output power and correspondingly, a reduction in weight is required for the piston ring.
Examples of materials having a specific gravity lower than the above-described iron-based material are aluminum alloys. In the existing circumstances, however, the aluminum alloy has a lower high-temperature strength and hence, if a piston ring is formed from the aluminum alloy, the tensile strength of the piston ring will be substantially reduced at a high temperature, e.g., 200.degree. to 300.degree. C. during operation of the engine, resulting in problems of increases in amounts of gas blown-by and oil consumed.
In addition, the intake valve has been formed from a heat resistant steel such as JIS SUH11 or the like.
Likewise, there is also a need for a reduction in weight for the intake valve. However, when a heat resistant steel is used as a material for forming the intake valve as in the prior art, there is a limit to the reduction in weight of the intake valve.